Previously, ladders have been made with little concern for basic safety. Standards have now been implemented that require a constraint which prevents the user from accidentally folding a ladder or step stool during use. The constraint must prevent an unintended fold up or collapse of the ladder or step stool. Such an unintended folding up of the ladder or step stool can result from a user running up to a ladder or walking briskly onto the ladder. The sideways force of the user can cause the ladder or step stool to fold or collapse. In other instances, the user may move to one side or the other and the resultant forces could cause the ladder to collapse or prematurely fold. The results can be very devastating. The user may fall and become injured. The items attached to the ladder or step stool may spill or fall. The items being carried by the user may also spill and fall causing further damage.
Several step stools and ladders now are provided with latches or other constraints. Some latches are for locking a bifurcated step into one of two positions. U.S. Pat. No. 4,485,892 teaches a locking mechanism for a platform stool which is used to lock a bifurcated step into one of two positions. U.S. Pat. No. 5,722,507 teaches a locking mechanism for a ladder which is used to lock a step into one of two positions. U.S. Pat. No. 5,762,163 also teaches locking mechanism for a step stool which is used to lock a bifurcated step into one of two positions. Both U.S. Pat. Nos. 5,722,507 and 5,762,163 are assigned to Cosco, Inc. of Columbus, Ind.
Some latches are for prevention of the collapse or premature folding of a ladder or step stool. The locking mechanisms shown are generally difficult to use. The latches are located below a step on the step stool or ladder and are generally not visible to the user. The user may unfold the step stool or ladder which may engage the lock or latch. However, since the latches or locks are hidden from view folding the ladder or step stool back into its collapsed or storage position may be a problem. Since the lock is not visible, users may become frustrated when trying to fold the ladder or step stool. Sometimes users feel the step stool or ladder is broken and resort to brute force to forcibly fold the step stool or ladder. This ruins the ladder or step stool or causes a loss in the structural integrity of the unit.
U.S. Pat. No. 6,390,237 was a significant improvement in latch design that prevents premature or undesirable folding. That patent also disclosed a latch that is readily visible when the ladder is in use and a ladder or step stool that is easy to store within the house. However, the latch of U.S. Pat. No. 6,390,237 required very tight tolerances in the manufacture of the ladder or step stool to function properly.
What is needed is an improved latch for a ladder or step stool that improves the operability of the mechanism while allowing for decreased tolerances during manufacture of the ladder or step stool.